The action threatens to leave students without the final marks they need to gain their degree, ruining their chances of graduating this summer.

It represents a dramatic escalation in the row between university leaders and rank-and-file lecturers amid claims the existing offer of a one per cent pay rise represents a real terms cut in wages.

Academics have already taken part in two national strikes last year and staged a series of brief two-hour walk-outs in late January and early February, although university leaders claim that turn out was low.

Rank-and-file lecturers have also been angered by a series of recent disclosures over vice-chancellors’ pay.

The Telegraph revealed last month that a number of university heads received double-digit pay rises last year – just as student tuition fees almost tripled to £9,000-a-year and lecturers received lower pay rises.

The Universities and Colleges Employers Association said lecturers had actually received an average three per cent pay rise when other merit awards were factored in this academic year.

It has criticised plans for a marking boycott.

But Sally Hunt, UCU general secretary, said: “A marking boycott is the ultimate sanction, but an avoidable one if the employers would negotiate with us over pay.

“No member I have spoken to wishes to see this dispute escalate, but in the continued absence of meaningful negotiations from the employers, we are left with no alternative.

“I fail to see how any university can claim to have students’ best interests at heart if it is not pushing for talks with the union to resolve this dispute.”

The UCU said the marking boycott would be launched on April 28 if no deal is made over pay.

A UCEA spokesman said institutions will "certainly be disappointed that the UCU is still threatening a marking boycott, as this is action that is once again aimed directly at students’ education".

"Both UCU and higher education institutions are well aware that strike support has dwindled still further in recent weeks, with the overwhelming majority of staff not taking part and having no wish to disrupt students’ education," he said.

"It is quite extraordinary for the UCU to be planning yet more action over last year’s pay uplifts with the 2014/15 pay negotiations due start in March, a full month prior to the start of their threatened marking boycott.

"Everyone is aware that last year’s pay uplifts, averaging three per cent, have already been paid. The employers were willing to explore whether both sides could engage in positive dialogue about how they could approach the 2014/15 pay round, rather than continue to dispute last year’s pay claim.

"Clearly higher education institutions will be affirming their policies for withholding full pay for any staff who follow such a damaging course of industrial action aimed at their students' education.”